Flow directing flaps in a gas turbine engine exhaust nozzle are subject to extremely harsh environmental conditions which have a significant impact on the design criteria of the overall flap arrangement and individual components. Exhaust gas temperatures may reach 4,000 F. or higher in the engine afterburning mode, requiring the use of temperature resistant materials and internal cooling to enable the gas contacting flap surfaces to withstand such temperatures for extended periods. The static gas pressure forces exerted on such flaps may range up to 50 psi (345 kPa) or greater depending upon the operational configuration of the nozzle and the current engine power output.
It is further desirable that such flaps be light in weight and easily disassembled for service or replacement. Disassembly is further complicated by the cramped clearances typically available within the nozzle for admitting workers, tools, etc.
In one design of a transversely extending flap in a thrust vectoring exhaust nozzle the flap is linked at the span ends to a pair of opposed sidewall disks which, under the influence of a positive internal static gas pressure, impart a resultant moment to the flap span ends for reducing the magnitude of the mid span flap deflection as fully explained in copending U.S. application Ser. No. 019,996 filed Feb. 27, 1987 by C. R. Stogner and W. M. Madden, titled "Exhaust Nozzle Flap Assembly". The combination of moment and shear forces at the span ends of such transversely oriented flaps results in a complicated pattern of stress at any joint located in such region, increasing the amount of reinforcing material, and hence weight, required to accommodate such forces as well as complicating the ducting of sufficient cooling gas into the flap interior.
What is needed is a simple, lightweight joint for securing an internally cooled flap in an exhaust nozzle of a gas turbine engine or the like.